When I got the car around 2.5 years ago at idle the oil pressure was at about 40 PSI. Now after it's been run for an hour or so on the freeway or whatnot it drops down to barely above the red zone at idle. Pressure looks fine while driving, however.

Anything I can do, short of a rebuild? Or do I just run thicker oil?

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Sootah.....could be the oil pump strainer or oil pump are on their way south. I would pull the pan and check to be sure the strainer isn;t clogged and go ahead and replace the pump while you are there. Good luck.

Phil

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87 FIERO GT 2.8 5spd

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Good advise above, but:
How many miles on the engine?
What oil and weight are you using?
Brand and type of filter you are using?
What is the engine temp when you see the low oil pressure reading?

You want to avoid heavy weight oils that are not multi-viscosity, as they will lead to more engine wear on cold starts. If you went to a heavier weight (10-50) multi-vis oil, 100% synthetic would be the best for prolonging the engine.

Make sure the oil level is correct. If it is to high it will "foam up" and cause low pressure.

It will also do it if the oil is old and need to be changed.

Cali Kid made some good points too. The viscosity is the key and it sounds as if yours is breaking down.

The temp will also play a major roll in viscosity, the warmer the engine the thinner the oil gets. I had a similuar problem with my 2.5 a while back and I changed the oil and eventually all the temp sensors. Now it runs normal but I can't pinpoint the exact problem since I changed everything at once including the pressure sender.

[This message has been edited by 84Bill (edited 12-19-2003).]

I did actually replace the pressure sending unit recently, and I don't remember noticing it before that. It may be that it was always this way and the old flaky (caused my fuel pump to run all the time) unit just never read the low pressure correctly.

What is the easiest way to drop the pan, and where is the screen at when I do it?

Thanks for your help. -Souter

Is your car a 2.5 liter 4cyl late 87 or 88? This same thing happened to me as well.. This is why im presently rebuilding my 88s engine. The Force Balancer for the 88 is driven off the crankshaft this in turn drives the oil pump. From what I was told by a helpful soul, is that there are no wear bearings on the force balancer and so when it wears out you will lose the drive to the oil pump slowly. My oil pressure dropped over time till one day coput and I had been searching for the cause in the same way. changing oils, changing filters.. checking strainers. Ive since removed the force balancer/oil pump and it had cracked from one side to the other throwing aluminum bits all about. Sadly i have no advice on how you could check if this is the problem, other then the obvious..low oil pressure with no obvious cause. Perhaps someone else will throw their two cents in.